This invention relates to an improvement in a bicycle freewheel assembly, and more particularly to protection of the freewheel assembly from dust and rain.
In general, a bicycle freewheel hub includes a hollow internal body and a hollow external body. The internal body is mounted on a rear wheel hub of a bicycle for corotation therewith. The external body, on which one or more sprocket are mounted, is relatively rotatable with respect to the internal body with the aid of a pair of bearing mechanism interposed therebetween. A ratchet mechanism is interposed between the internal body and the external body so that a driving force produced by a cyclist's forward pedalling is transmitted via a drive chain, the sprocket and the external body to the internal body and so that the external body is free from corotation with the internal body during the cyclist's back pedalling. Thus, the external body is radially spaced apart from the internal body to form an internal space for accommodating the pair of bearing mechanisms and the ratchet mechanism.
Therefore, dust and/or rain intrude into the inside of the freewheel assembly through a gap between the external body and the internal body thereby to cause deterioration in function of the bearing mechanisms and the ratchet mechanism. It may appear that such problem can be easily solved by provision of a suitable cover to seal the gap between the external body and the internal body. However, the problem is, in fact, not so simple because the external body must be relatively rotatable with respect to the internal body and because there are strict dimensional restrictions with respect to various portions of the external body and also those of the internal body if the freewheel assembly is designed to meet the requirements of International Industrial Standard and/or Japanese Industrial Standard.
Under such situations, a bicycle freewheel provided with a satisfactory means for preventing the intrusion of dust and/or rain into the gap between the external body and the internal body is not available at present in the commercial market.
It is, therefore, an object of the invention is to provide an improved bicycle freewheel assembly provided with a protective arrangement for minimizing undesirable intrusion of dust and/or rain into the inside of the bicycle freewheel assembly.
Another object of the invention is to provide an improved bicycle freewheel assembly provided with the above mentioned protective arrangement without any substantial change in dimension of the freewheel assembly.
Other objects, features and advantages of the invention will become apparent from the following detailed description.
According to the invention, there is provided a bicycle freewheel assembly comprising a hollow external body relatively rotatable with and radially spaced apart from a hollow internal body, a first dust protective member including a horizontal tubular body and an annular vertical flange and secured to the alternative of the internal body or the external body at one side of the the freewheel assembly, a second dust protective member including a horizontal tubular body and an annular vertical flange and secured to the alternative of the external body or a lock nut mounted on the internal body at the other side of the freewheel assembly, a first narrow clearance formed between the first dust protective member and the alternative of the internal body or the external body at the one side of the freewheel assembly, a second narrow clearance formed between the second dust protective member and the alternative of the external body or the lock nut at the other side of the freewheel assembly, and each of the first and the second clearances being L-shaped or hook-shaped to minimize undesirable intrusion of dust and/or rain into the inside of the freewheel assembly.